Use JComboBox as JTree's node cell editor

• download example.jar
• download src.zip
• repository

Code

class PluginCellEditor extends DefaultCellEditor {
  private final PluginPanel panel;
  private transient PluginNode node;

  protected PluginCellEditor(JComboBox comboBox) {
    super(comboBox);
    panel = new PluginPanel(comboBox);
  }
  @Override public Component getTreeCellEditorComponent(
      JTree tree, Object value, boolean isSelected, boolean expanded,
      boolean leaf, int row) {
    this.node = panel.extractNode(value);
    return panel;
  }
  @Override public Object getCellEditorValue() {
    Object o = super.getCellEditorValue();
    return Optional.ofNullable(node).map(node -> {
      DefaultComboBoxModel m =
        (DefaultComboBoxModel) panel.comboBox.getModel();
      PluginNode n = new PluginNode(panel.pluginName.getText(), node.plugins);
      n.setSelectedPluginIndex(m.getIndexOf(o));
      return (Object) n;
    }).orElse(o);
  }
  @Override public boolean isCellEditable(EventObject e) {
    Object source = e.getSource();
    if (!(source instanceof JTree) || !(e instanceof MouseEvent)) {
      return false;
    }
    JTree tree = (JTree) source;
    Point p = ((MouseEvent) e).getPoint();
    TreePath path = tree.getPathForLocation(p.x, p.y);
    if (Objects.isNull(path)) {
      return false;
    }
    Object node = path.getLastPathComponent();
    if (!(node instanceof DefaultMutableTreeNode)) {
      return false;
    }
    Rectangle r = tree.getPathBounds(path);
    if (Objects.isNull(r)) {
      return false;
    }
    Dimension d = panel.getPreferredSize();
    r.width = d.width;
    if (r.contains(p)) {
      showComboPopup(tree, p);
      return true;
    }
    return delegate.isCellEditable(e);
  }
  private void showComboPopup(JTree tree, Point p) {
    EventQueue.invokeLater(() -> {
      Point pt = SwingUtilities.convertPoint(tree, p, panel);
      Component o = SwingUtilities.getDeepestComponentAt(panel, pt.x, pt.y);
      if (o instanceof JComboBox) {
        panel.comboBox.showPopup();
      } else if (Objects.nonNull(o)) {
        Container c = SwingUtilities.getAncestorOfClass(
            JComboBox.class, (Component) o);
        if (c instanceof JComboBox) {
          panel.comboBox.showPopup();
        }
      }
    });
  }
}

References

• java - JTree selection issue - Stack Overflow
• Use JComboBox as JTree's node cell editor(Japanese)